use base64::{engine::general_purpose, Engine as _};
use hmac::{Hmac, Mac};
use sha2::Sha256;
use std::collections::HashMap;
use std::process::Stdio;
use std::time::Duration;
use tauri::{Manager, Runtime, State};
use tokio::io::{AsyncBufReadExt, BufReader};
use tokio::process::Command;
use tokio::sync::mpsc;
use tokio::time::Instant;

use crate::device::{get_devices_from_backend, DeviceInfo};
use crate::error::{ErrorCode, LlamacppError, ServerError, ServerResult};
use crate::path::{validate_binary_path, validate_model_path, validate_mmproj_path};
use crate::process::{
    find_session_by_model_id, get_all_active_sessions, get_all_loaded_model_ids,
    get_random_available_port, is_process_running_by_pid,
};
use crate::state::{LLamaBackendSession, LlamacppState, SessionInfo};
use jan_utils::{
    extract_arg_value, parse_port_from_args, setup_library_path, setup_windows_process_flags,
};

#[cfg(unix)]
use crate::process::graceful_terminate_process;

#[cfg(all(windows, target_arch = "x86_64"))]
use crate::process::force_terminate_process;

type HmacSha256 = Hmac<Sha256>;

#[derive(serde::Serialize, serde::Deserialize)]
pub struct UnloadResult {
    success: bool,
    error: Option<String>,
}

/// Load a llama model and start the server
#[tauri::command]
pub async fn load_llama_model<R: Runtime>(
    app_handle: tauri::AppHandle<R>,
    backend_path: &str,
    library_path: Option<&str>,
    mut args: Vec<String>,
    envs: HashMap<String, String>,
) -> ServerResult<SessionInfo> {
    let state: State<LlamacppState> = app_handle.state();
    let mut process_map = state.llama_server_process.lock().await;

    log::info!("Attempting to launch server at path: {:?}", backend_path);
    log::info!("Using arguments: {:?}", args);

    validate_binary_path(backend_path)?;

    let port = parse_port_from_args(&args);
    let model_path_pb = validate_model_path(&mut args)?;
    let _mmproj_path_pb = validate_mmproj_path(&mut args)?;

    let api_key: String;

    if let Some(api_value) = envs.get("LLAMA_API_KEY") {
        api_key = api_value.to_string();
    } else {
        log::warn!("API key not provided");
        api_key = "".to_string();
    }

    let model_id = extract_arg_value(&args, "-a");

    // Configure the command to run the server
    let mut command = Command::new(backend_path);
    command.args(args);
    command.envs(envs);

    setup_library_path(library_path, &mut command);
    command.stdout(Stdio::piped());
    command.stderr(Stdio::piped());
    setup_windows_process_flags(&mut command);

    // Spawn the child process
    let mut child = command.spawn().map_err(ServerError::Io)?;

    let stderr = child.stderr.take().expect("stderr was piped");
    let stdout = child.stdout.take().expect("stdout was piped");

    // Create channels for communication between tasks
    let (ready_tx, mut ready_rx) = mpsc::channel::<bool>(1);

    // Spawn task to monitor stdout for readiness
    let _stdout_task = tokio::spawn(async move {
        let mut reader = BufReader::new(stdout);
        let mut byte_buffer = Vec::new();

        loop {
            byte_buffer.clear();
            match reader.read_until(b'\n', &mut byte_buffer).await {
                Ok(0) => break, // EOF
                Ok(_) => {
                    let line = String::from_utf8_lossy(&byte_buffer);
                    let line = line.trim_end();
                    if !line.is_empty() {
                        log::info!("[llamacpp stdout] {}", line);
                    }
                }
                Err(e) => {
                    log::error!("Error reading stdout: {}", e);
                    break;
                }
            }
        }
    });

    // Spawn task to capture stderr and monitor for errors
    let stderr_task = tokio::spawn(async move {
        let mut reader = BufReader::new(stderr);
        let mut byte_buffer = Vec::new();
        let mut stderr_buffer = String::new();

        loop {
            byte_buffer.clear();
            match reader.read_until(b'\n', &mut byte_buffer).await {
                Ok(0) => break, // EOF
                Ok(_) => {
                    let line = String::from_utf8_lossy(&byte_buffer);
                    let line = line.trim_end();

                    if !line.is_empty() {
                        stderr_buffer.push_str(line);
                        stderr_buffer.push('\n');
                        log::info!("[llamacpp] {}", line);

                        // Check for readiness indicator - llama-server outputs this when ready
                        let line_lower = line.to_string().to_lowercase();
                        if line_lower.contains("server is listening on")
                            || line_lower.contains("starting the main loop")
                            || line_lower.contains("server listening on")
                        {
                            log::info!("Model appears to be ready based on logs: '{}'", line);
                            let _ = ready_tx.send(true).await;
                        }
                    }
                }
                Err(e) => {
                    log::error!("Error reading logs: {}", e);
                    break;
                }
            }
        }

        stderr_buffer
    });

    // Check if process exited early
    if let Some(status) = child.try_wait()? {
        if !status.success() {
            let stderr_output = stderr_task.await.unwrap_or_default();
            log::error!("llama.cpp failed early with code {:?}", status);
            log::error!("{}", stderr_output);
            return Err(LlamacppError::from_stderr(&stderr_output).into());
        }
    }

    // Wait for server to be ready or timeout
    let timeout_duration = Duration::from_secs(180); // 3 minutes timeout
    let start_time = Instant::now();
    log::info!("Waiting for model session to be ready...");
    loop {
        tokio::select! {
            // Server is ready
            Some(true) = ready_rx.recv() => {
                log::info!("Model is ready to accept requests!");
                break;
            }
            // Check for process exit more frequently
            _ = tokio::time::sleep(Duration::from_millis(50)) => {
                // Check if process exited
                if let Some(status) = child.try_wait()? {
                    let stderr_output = stderr_task.await.unwrap_or_default();
                    if !status.success() {
                        log::error!("llama.cpp exited with error code {:?}", status);
                        return Err(LlamacppError::from_stderr(&stderr_output).into());
                    } else {
                        log::error!("llama.cpp exited successfully but without ready signal");
                        return Err(LlamacppError::from_stderr(&stderr_output).into());
                    }
                }

                // Timeout check
                if start_time.elapsed() > timeout_duration {
                    log::error!("Timeout waiting for server to be ready");
                    let _ = child.kill().await;
                    let stderr_output = stderr_task.await.unwrap_or_default();
                    return Err(LlamacppError::new(
                        ErrorCode::ModelLoadTimedOut,
                        "The model took too long to load and timed out.".into(),
                        Some(format!("Timeout: {}s\n\nStderr:\n{}", timeout_duration.as_secs(), stderr_output)),
                    ).into());
                }
            }
        }
    }

    // Get the PID to use as session ID
    let pid = child.id().map(|id| id as i32).unwrap_or(-1);

    log::info!("Server process started with PID: {} and is ready", pid);
    let session_info = SessionInfo {
        pid: pid.clone(),
        port: port,
        model_id: model_id,
        model_path: model_path_pb.display().to_string(),
        api_key: api_key,
    };

    // Insert session info to process_map
    process_map.insert(
        pid.clone(),
        LLamaBackendSession {
            child,
            info: session_info.clone(),
        },
    );

    Ok(session_info)
}

/// Unload a llama model by terminating its process
#[tauri::command]
pub async fn unload_llama_model<R: Runtime>(
    app_handle: tauri::AppHandle<R>,
    pid: i32,
) -> ServerResult<UnloadResult> {
    let state: State<LlamacppState> = app_handle.state();
    let mut map = state.llama_server_process.lock().await;

    if let Some(session) = map.remove(&pid) {
        let mut child = session.child;

        #[cfg(unix)]
        {
            graceful_terminate_process(&mut child).await;
        }

        #[cfg(all(windows, target_arch = "x86_64"))]
        {
            force_terminate_process(&mut child).await;
        }

        Ok(UnloadResult {
            success: true,
            error: None,
        })
    } else {
        log::warn!("No server with PID '{}' found", pid);
        Ok(UnloadResult {
            success: true,
            error: None,
        })
    }
}

/// Get available devices from the llama.cpp backend
#[tauri::command]
pub async fn get_devices(
    backend_path: &str,
    library_path: Option<&str>,
    envs: HashMap<String, String>
) -> ServerResult<Vec<DeviceInfo>> {
    get_devices_from_backend(backend_path, library_path, envs).await
}

/// Generate API key using HMAC-SHA256
#[tauri::command]
pub fn generate_api_key(model_id: String, api_secret: String) -> Result<String, String> {
    let mut mac = HmacSha256::new_from_slice(api_secret.as_bytes())
        .map_err(|e| format!("Invalid key length: {}", e))?;
    mac.update(model_id.as_bytes());
    let result = mac.finalize();
    let code_bytes = result.into_bytes();
    let hash = general_purpose::STANDARD.encode(code_bytes);
    Ok(hash)
}

/// Check if a process is still running
#[tauri::command]
pub async fn is_process_running<R: Runtime>(
    app_handle: tauri::AppHandle<R>,
    pid: i32,
) -> Result<bool, String> {
    is_process_running_by_pid(app_handle, pid).await
}

/// Get a random available port
#[tauri::command]
pub async fn get_random_port<R: Runtime>(app_handle: tauri::AppHandle<R>) -> Result<u16, String> {
    get_random_available_port(app_handle).await
}

/// Find session information by model ID
#[tauri::command]
pub async fn find_session_by_model<R: Runtime>(
    app_handle: tauri::AppHandle<R>,
    model_id: String,
) -> Result<Option<SessionInfo>, String> {
    find_session_by_model_id(app_handle, &model_id).await
}

/// Get all loaded model IDs
#[tauri::command]
pub async fn get_loaded_models<R: Runtime>(
    app_handle: tauri::AppHandle<R>,
) -> Result<Vec<String>, String> {
    get_all_loaded_model_ids(app_handle).await
}

/// Get all active sessions
#[tauri::command]
pub async fn get_all_sessions<R: Runtime>(
    app_handle: tauri::AppHandle<R>,
) -> Result<Vec<SessionInfo>, String> {
    get_all_active_sessions(app_handle).await
}

/// Get session information by model ID
#[tauri::command]
pub async fn get_session_by_model<R: Runtime>(
    app_handle: tauri::AppHandle<R>,
    model_id: String,
) -> Result<Option<SessionInfo>, String> {
    find_session_by_model_id(app_handle, &model_id).await
}